2 and 5 look either out of focus or enlarged beyond their limits. If it's the later case get Genuine Fractal or Alien Skin's BlowUp.
Number 4 has sharpening halo and color fringing. In a shot like that it's easy to fix the colored aberrations by using the Hue/Saturation tool in Colorize mode. And I don't know an easy way of removing sharpening halo once it's introduced.
All great shots though! You have a great eye for balance and composition!
Heya Garbear, welcome to ThePhotoForum.
Did you use your digital zoom in order to take both Photos 2 and 5? If so: better don't. The outcome isn't good. You get a close photo, but you "pay" for it with loss of sharpness.
Digital zoom is not much else but an in-camera crop of a photo, so resolution suffers heaps.
My favourite here is the third.
You have an eye for subjects and a good feeling of how to frame them pleasantly!